This paper presents a discussion of the development of a viscous fan clutch with continuous linear variable speed control function for engine cooling system to reduce cooling fan noise and improve the overall fuel efficiency of the engine. It is well known generally that the operation of the engine cooling fan is one of the major noise and vibration sources in an engine as well as the major power consumption device in engine. By applying a fan drive clutch having a continuous speed control device providing the proper cooling air flow rate proportional to engine cooling load, it can be expected that the fan driving horsepower can be reduced and also fan noise and vibration can be reduced significantly. In the present study it is shown that a viscous fluid fan clutch, for small and medium diesel engines (1 to 3.5 ton class), having a linear variable speed control function corresponding to cooling load and low temperature hysteresis has been developed. The results obtained show that the proposed design viscous fluid fan clutch can reduce the engine fan operational noise and vibration as well as the cooling fan driving horsepower significantly.